What if the government installed a GPS device in every car and taxed everyone based on the miles they drove?

It may sound like science fiction, but that's exactly what's being proposed in a study likely to be given the green light by the Metropolitan Transportation Commission and the Association of Bay Area Governments later this week.

The idea is called a vehicle miles traveled (VMT) tax, and government administrators around the country are increasingly thinking about it as a way for pay for necessary transportation infrastructure improvements.

"I don't want to say it's pie in the sky. A VMT charge is really an option for the future to be looked at and considered," said Randy Rentschler, spokesman for the Metropolitan Transportation Commission, the agency leading the effort. He said realistically the plan is so complex it might take a decade to implement if the public buys in.

Under the early proposal, the VMT tax could cost up to a dime per mile, or the cost may peak during rush hour and bottom out, perhaps to less than a penny per mile, when no one's on the roads.

The study is part of Plan Bay Area, a comprehensive, nine-county land use, transportation and housing plan that aims to slow the increase of local greenhouse gas emissions as the Bay Area's population swells.

As Americans switch to more fuel efficient automobiles, like gas-electric hybrids or plug-in electrics, they buy less gas and. As a result, they pay a lower amount in gas taxes while still causing the same wear and tear on roads the gas tax largely goes to maintain. Gas taxes discourage fuel consumption--which is good for combating global warming--but do a poor job of accurately pricing each individual motorist's use of the nation's highways.

Thus the logic behind a VMT tax.

"The current indirect user fee system based on taxes paid for fuel consumed provides users with only weak price signals to use the transportation system in the most efficient ways," said a 2009 report by the National Surface Transportation Infrastructure Financing Commission that came out strongly in favor of instituting a national VMT tax.

The Obama Administration ultimately put the brakes on the commission's proposal.

The difficulty with a VMT is largely in the enforcement; it requires either a self-reporting of total miles driven (something that's easy to conveniently underestimate) or the government's tracking all the cars on the road, a move that's sure to raise the hackles of civil libertarians.

The problem is in the implementation: it’s hard to have a compulsory VMT tax, since that involves attaching some kind of meter to every American’s car, and Americans are not going respond well to that idea. Hell, even New York cabbies went on strike to protest GPS devices being put in their vehicles to track their every movement.

While a VMT tax in the Bay Area is a long way off (the study looking into its feasibility has yet to be officially approved), other regions of the country are significantly further along in the process. The Oregon Department of Transportation is rolling out a VMT pilot program this fall.

Check out this video of Rep. Earl Blumenaur (D-OR) advocating a VMT tax on the floor of the house: